Previous clinical observations have suggested that with increased age, decremental changes in salivary gland function occur. To study the mechanism of this alteration in animal models, salivary gland functions from young adult and aged male and female rats have been characterized biochemically and regulation by neutrotransmitters has been investigated. Included are studies of: (1) protein secretion from the parotid gland, and its control by the beta-adrenergic system (beta-receptor) characteristics, hormone responsiveness, cAMP-dependent protein kinase, endogenous phosphorylation); and (2) fluid and electrolyte secretion (K efflux, alpha-adrenergic and cholinergic responsiveness) from the parotid gland. Additionally, examination of intermediary metabolic function (glucose oxidation) of the parotid gland has been initiated (basal; stimulated by adrenergic and cholinergic agonists). In the submandibular gland, basal protein and mucin biosynthesis and release, as well as stimulated exocrine release beta-adrenergic) have been investigated. Biochemical characterization of submandibular gland exocrine products has begun.